and channel spacing can be controlled by appropriately tuning two pump wavelengths. With further improvements, both theories and experiments are under way to study the tuning bandwidth of two pumps and evaluate the impact of the signal and two pump powers on the conversion efficiency of dual-channel idler waves.
5. Conclusions
All-optical single-to-dual channel wavelength conversion has been experimentally verified by exploiting SFGΟ©DFG in PPLN waveguides. A 40 Gbit/s nonreturn-to-zero signal is adopted. Dual-channel idler waves can be achieved by setting pump2 wavelength close to the signal or pump1 wavelength so that two SFGΟ©DFG interactions take place in the PPLN waveguide. Wavelength relationships between dual-channel idler waves and three incident waves are studied when the wavelength of pump2 is near the signal wavelength. It is found that dual-channel idler wavelengths are symmetric relative to the pump1 wavelength and the channel spacing between idler1 and idler2 is twice the span from pump2 to signal. Therefore, it is possible to change dual-channel idler wavelengths and channel spacing by properly tuning two pump wavelengths. The results obtained will stimulate further theoretical and experimental investigations on single-to-dual and single-to-multiple channel wavelength conversions.